Utility Plant Components of Utility Plant (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land	$ 14,935	$ 15,120
Source of Supply	51,077	38,448
Pumping Equipment	53,080	51,639
Water Treatment	121,561	129,428
Public Utilities, Property, Plant and Equipment, Transmission and Distribution	646,081	605,587
General Plant	97,798	88,492
Plant Held for Future Use Amount	304	219
Acquisition Adjustment	(1,616)	(1,644)
Utility Plant	$ 983,220	$ 927,289